1. Field of the Invention
The present invention relates to engine starter gearing for an engine and more particularly to engine starter gearing of a positive shift type, including a dentil clutch to provide driving and overrunning features and further including provisions for effecting the automatic separation of the clutch teeth after the engine becomes self-running.
2. Description of the Prior Art
The present invention is an improvement over U.S. Pat. No. 4,712,435, entitled "Engine Starter Gearing," issued Dec. 15, 1987, to Losey et al and assigned to the assignee hereof, as well as a further improvement over the starter gearing system described in U.S Pat. No. 3,263,509 entitled "Engine Starter Drive" and issued Aug. 2, 1966, to James Digby. The Digby patent disclosed an engine starter gearing using centrifugal weights and a conical thrust washer for separating dentil clutch teeth after engine start-up to prevent long periods of clutch overrunning and accompanying deleterious wear on the clutch teeth. An annular recess is formed in the driven clutch member. A circular recess is provided in the face of the driven clutch member facing the driving clutch member. An annular thrust washer is fitted in the recess and abuts the driving clutch member. A conical surface is provided in the annular thrust washer facing the driven clutch member. A plurality of centrifugal flyweight members are also provided in the circular recess. The centrifugal flyweight members are provided with an inclined surface cooperating with the conical surface in the annular thrust washer, such that, when an overrunning condition occurs, the centrifugal flyweight members move outwardly and the inclined surface engages the conical surface of the annular thrust washer so as to bias the driving clutch member away from the driven clutch member. The centrifugal flyweight members are prevented from axial or rotational movement with respect to the driven clutch member by pins extending through suitable bores in the driven clutch member and the centrifugal flyweight member.
While the engine starter gearing of Digby has been satisfactory in operation, it is difficult and expensive to assemble. This is true because a plurality of movable pins and centrifugal flyweight members must be somehow maintained in position relative to the driven clutch member during the assembly of the driven clutch member to the driving clutch member. Furthermore, the weight and, therefore, the effectiveness of the centrifugal flyweight members is reduced by the existence of a substantial bore therethrough, in comparison to the size of the centrifugal flyweight member, for admission of the pin. The bore through the centrifugal flyweight members further reduces the strength of the flyweight members and, accordingly, limits the materials and dimensions which may advantageously be used for the centrifugal flyweight members.
The embodiment of FIGS. 3 and 4 of the aforesaid U.S. Pat. No. 4,712,435, entitled "Engine Starter Gearing," issued Dec. 15, 1987, to Losey et al solved many of the aforesaid engine starter gearing disadvantages, but such embodiment requires the use of a driven clutch member which is difficult to machine.
What is needed, therefore, is an improved engine starter gearing using a centrifugal flyweight clutch separator which is easier and less expensive to assemble. Furthermore, what is needed is such an engine starter gearing having a more solid, compact, and durable configuration for the centrifugal flyweight member, which simplifies the manufacturing operations involved in manufacturing such engine starter gearing, particularly in regard to the driven clutch member component thereof.